Conventionally, there is a well-known centrifugal governor provided in a diesel engine, wherein the centrifugal governor comprises a governor shaft driven by a crankshaft through gears and the like, and a governor weight disposed around the governor shaft and connected to a governor lever through a sleeve. The governor lever is connected to a control rack of a fuel injection pump.
In this construction, when the engine is started and engine speed is increased, the governor weight is opened by centrifugal force and the sleeve is slid. Accordingly, the governor lever is turned and the control rack is slid in its fuel decreasing direction, thereby decreasing the injection rate of the fuel injection pump. On the contrary, when the engine speed is decreased and the centrifugal force applied on the governor weight is decreased, the governor weight is closed by a spring biasing the governor weight to the opposite direction, thereby sliding the control rack of the fuel injection pump in its fuel increasing direction.
The governor also has a limiter for controlling the turning of the governor lever so as to prevent the fuel injection rate from being over or under the set value. The fuel injection rate is maximum at the start of driving an engine, and after the engine speed arises to some degree, the fuel injection rate is decreased. When a certain engine speed is reached, reduction of the fuel injection rate is stopped. Afterward, the injection rate is kept constant until engine speed reaches the maximum. For example, the Japanese Patent Laid Open Gazette Hei. 10-227234 discloses a limiter lever for controlling the turning of the governor lever within a fixed range, wherein a stopper bolt is provided to demarcating the maximum turning degree of the limiter lever. When the output of the engine is set to its upper limit by a regulator handle, the stopper bolt abuts against the limiter lever so as to demarcate the position of the limiter lever. In this way, the limiter lever is located so as to control the turning range of the governor lever between the injection rate increasing direction and the injection rate decreasing direction.
The position of the above limiter should be determined so as to get the best fuel injection rate in consideration of combustion efficiency and restriction of exhaust emission. However, the best fuel injection rate changes depending on the temperature of an engine. When engine speed is increased in a warm condition, combustion efficiency of the engine is high so that low fuel injection rate is desired so as to reduce exhaust emission. However, when increasing engine speed with fuel injection of this low rate in a cold condition, combustion efficiency of the engine is reduced so that a long time is required to increase the engine speed to its rated value.
Therefore, the position of the limiter is desired to be adjustable corresponding to the temperature of the engine. However, in the above-mentioned disclosed art, it is unreasonable to adjust the position of the stopper bolt corresponding to variation of engine temperature. Therefore, in fact, the time for starting up an engine, i.e., for increasing the rotational speed of a started engine is changed with temperatures.